May 21, 2014

Many Healthy Americans Harbor Human Papilloma Viruses

There are currently 148 known strains of the human papillomavirus (HPV), and a new study led by NYU Langone Medical Center reveals that 69 percent of otherwise healthy US adults are infected with one or more strains.

The findings, presented at the 2014 American Society for Microbiology Meeting, are derived from what is believed to be the largest and most detailed genetic analysis of its kind. The analysis showed that, out of the 103 people whose DNA was publically available through a government database, they found 109 strains of HPV. Only four participants had either of the two HPV strains known to cause most cases of cervical cancer, some throat cancers, and genital warts.

The majority of the 109 strains appear to be harmless, so far, and can remain dormant in the body for years. In the body, where many viral strains keep each other in check to prevent other strains from spreading uncontrollably, the overwhelming presence of HPV indicates a delicate balancing act. Researchers are increasingly aware that HPV can be spread through skin-to-skin contact, however it remains the most common sexually transmitted infection (STI) in the US — so common, in fact, that if estimates are correct, nearly all men and women contract some strain of it during their lives.

"Our study offers initial and broad evidence of a seemingly 'normal' HPV viral biome in people that does not necessarily cause disease and that could very well mimic the highly varied bacterial environment in the body, or microbiome, which is key to maintaining good health," says NYU Langone pathologist and associate professor Zhiheng Pei, who presented the findings this week.

NYU Langone research scientist Yingfei Ma, PhD, said "the HPV 'community' in healthy people is surprisingly more vast and complex than previously thought, and much further monitoring and research is needed to determine how the various non-cancer-causing HPV genotypes interact with the cancer-causing strains, such as genotypes 16 and 18, and what causes these strains to trigger cancer."

During the two-year study, the research team analyzed data obtained from the National Institutes of Health (NIH) Human Microbiome Project. The project gathers information on the effect microorganisms have on human health.

The NIH researchers used a technique called shotgun sequencing to assemble a comprehensive DNA analysis of the samples. Shotgun sequencing allowed the research team to sort through vast amounts of genetic material contained in the 748 tissue swabs. The tissue samples were collected from the major organs (skin, mouth, vagina, and gut) of healthy participants ages 18 to 80. Shotgun sequencing deciphers the genetic code of long strands of DNA in a random firing pattern.

Until the harm or benefits of the many HPV strains can be understood, Dr. Pei cautions that people should not be overly concerned. To understand any potential threat before seeking treatment, he suggests that they consult with their clinician or an infectious disease specialist. Pei also recommends getting vaccinated against types 16 and 18 to prevent cervical cancer until a broader anti-HPV vaccine becomes available to target other harmful effects.

• Seventy-one participants were infected. Of these, 42 had HPV in only one organ (59 percent), 22 had it in two organs (31 percent), and seven had it in three (10 percent). None had HPV infections in all four organs tested.

• The most varied strains of HPV were found in the skin samples (80 types total, with 40 that were only found in skin). The second highest number was found in vaginal tissue 43 types of HPV, with 20 strains exclusive to the organ), followed by mouth tissue (33 types, of which five were exclusively oral in origin), and gut tissue (six types, all of which were found in other organs).

The findings illustrate the weaknesses in current clinical testing for HPV, which are designed to recognize only around a dozen of the viral types most closely tied to cervical cancer. To more accurately assess people's true HPV infection status, Pei says that broader detection methods are necessary.

Dr. Ma says that the research team intends to continue their investigations by determining which non-cancer-causing strains of HPV might play a role in cancers of the cervix, mouth and skin, as well as developing more comprehensive diagnostic testing kits to detect all strains of HPV.